The Iowa Lottery is on a roll with sales rising 11 percent over a year ago, but there are worries that ticket-buying could suddenly plunge if gasoline prices exceed $4 a gallon.

The fear is that Iowa motorists will have fewer discretionary dollars in their pockets to spend on Powerball and other games if gasoline prices spike. That’s a trend seen in past years when gasoline prices soared.

“We are thinking that $4 to $4.50 per gallon would definitely hit us, but up to that point I am not as concerned,” said Iowa Lottery Chief Executive Officer Terry Rich.

He called $5 a gallon gasoline “uncharted territory,” adding it would be difficult to assess the impact on lottery sales.

For the seven months ending Jan. 31, the Iowa Lottery had gross sales of $169.5 million, up sharply from $152.1 million for the same period a year ago.

“January sales were high due to scratch sales and the introduction of $2 Powerball,” Rich said. But pull-tabs, the lottery’s main business at taverns, continue to be negatively affected by competition from amusement machines installed at taverns, he said.

Since the state fiscal year began July 1, the Iowa Lottery has generated $42.6 million in profits, up 9.1 percent compared to the previous fiscal year. The proceeds are turned over to the state’s general fund for state government programs, and to a trust for military veterans programs.